A. Field of the Invention
The present invention relates to a wafer probing test machine, more specifically, to a wafer prober to clean probe card in-line by spraying three phases of CO2.
B. Description of the Related Art
In the course of testing wafers of semiconductor devices, pads of wafer chip are contacted with probe-card to test or examine whether or not the electric circuit on each chip is disconnected and also to test electric characteristics of each chip. The wafer probing test machine (or wafer prober) is used for this wafer test.
FIGS. 1 and 2 illustrate a typical testing apparatus 100 including a prober 120, a test head 130 and a tester 150. The testing apparatus 100 is used to test the performance of a die on a wafer. As illustrated, a probe card 140 sits below and in contact with test head 130. During testing, the prober 120 supports the wafer 123 on a chuck 122 and positions the wafer 123 so as to precisely align the bond pads of a die to be tested with the probe tips 142 on the probe card 140. The chuck 122 is connected to a staging device 124 by rods 121.
The staging device 124 typically positions the chuck 122 along a x-y-z plane by moving along a stage floor 125 on a ball screw stage assembly (not shown). The chuck 122 typically includes a vacuum chuck wherein the wafer 123 being tested is held in position by drawing a vacuum within a plurality of interconnecting channels (not shown) that are formed within the surface of the chuck. Once aligned, chuck 122 is raised via rods 121 such that the bond pads of the die on the wafer 123 are forced against the probe tips 142 on the probe card 140.
Typically, the bond pads of the die on the wafer 123 are made of metallic materials, such as aluminum, which can oxidize when exposed to air. Also, organic material left over from certain fabrication processes can be disposed on the bond pads. When probe card tips 142 repeatedly contact bond pads on the wafer 123, metal oxides such as aluminum oxides and other materials on the bond pads can build-up on the probe card tips 142, as illustrated in FIG. 3. Thereby the materials built-up on the probe card tips 142 interfere with the function of the probe pins during testing operations. Thus, it becomes necessary to periodically clean the probe pins on a probe card.
In conventional cleaning operations, a probe maintenance station is utilized in order to clean probe pins on a probe card used in testing fabricated semiconductor device. This requires the removal of the probe card from the production line in order to clean the probe pins and then results in a certain amount of production downtime. The production downtime includes the time to remove the probe card from the prober, and the time to install and perform a complete new set up for a clean probe card. Also, as manufacturing techniques have improved, it has become possible to probe more semiconductor dies in parallel at one time and therefor requires increasingly wider probe card arrays. This has resulted in ever increasing difficulty and downtime in order to have the probe card arrays taken off-line, to replace the probe card arrays, and then to bring the system back on-line, as well as additional time to clean the removed probe card arrays and bring the arrays back into the service.
Accordingly, there is a need for improving probe pin cleaning systems and methods that overcome or avoid the above problems.
It is an object of present invention to provide a wafer prober capable of cleaning probe pins in-line, which employs sprayer, such as CO2 triple point sprayer, to in-line clean the probe pins on probe card.
According to one aspect of the present invention, the wafer prober capable of cleaning probe pins in-line according to the present invention is used in the wafer probing test system having a test machine and a test head. The wafer prober includes a housing having a probe card holder for holding a probe card, a staging device installed in the housing and moving along a X-Y-Z plane, and a chuck installed on the staging device for holding a wafer to be tested. The chuck further includes at least a nozzle installed at the staging device for cleaning probe pins of the probe card by spraying solid, vapor and liquid CO2.
Since the wafer probing test system according to the present invention does not need to remove the probe card away from the prober to clean, and does not need to position the probe card again, the production downtime can be greatly reduced. Additionally, due to that the wafer probing test system employs the nozzle to spray out three phases of CO2 to clean the probes, the probes do not be damaged and the lifetime of the probe can be extended.